Such known devices comprise as the means for feeding off the stack a device for translating the mail pieces, formed for example by a rotary perforated drum in which a partial vacuum is created and which entrains the first mail piece with a speed V.sub.1. A transfer device is located downstream from the means for feeding off the stack, this transfer device acting at a speed V.sub.2 identical with V.sub.1. A device for avoiding double feeds is usually located between these two devices, being formed by a brush means or by a hinged flap.
As a general rule, anti double feed devices do not work efficiently.
This is mainly the case when the mail pieces being handled are unsealed objects, of the nature of publicity or other brochures. These brochures may be composed for example of a sheet folded into several panels or of several leaves connected together like a small booklet. Any conventional device for feeding from a stack and based on braking the mail piece coming off in a double feed, then works badly and causes buckling or tearing of the mail pieces fed off the stack.
The invention enables these problems in feeding off a stack and of double feeds of unsealed mail pieces to be overcome.